Latent hardener with improved barrier properties and compatibility

ABSTRACT

A curing agent for epoxy resins that is comprised of the reaction product of an amine, an epoxy resin, and an elastomer-epoxy adduct; compositions containing the curing agent and an epoxy resin; the compositions are useful in electronic displays, circuit boards, semi conductor devices, flip chips and other applications.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application Ser.No. 61/313,199 filed Mar. 12, 2010, the contents of which are herebyincorporated by reference.

FIELD OF THE INVENTION

This invention relates to latent hardeners for epoxy resins and, moreparticularly, to latent hardeners comprised of a core material that isencapsulated or coated in a step-wise manner with two or more shellmaterials.

BACKGROUND OF THE INVENTION

Epoxy adhesives have been known for over 50 years and were one of thefirst high temperature adhesives to become commercialized. Once cured,the material retains its adhesive properties over a large range oftemperatures, has high shear strengths, and is resistant to weathering,oil, solvents, and moisture. The adhesive is available commercially aseither a 1-part adhesive or 2-part adhesive and is available in severalforms, such as pastes, solvent solutions, and supported films. Of thethree forms, the 1-part adhesive film generally provides good adhesivestrength with better thickness uniformity and has found practical use inthe development of anisotropic conducting films for electronics, mostnotably flat panel displays.

To construct a 1-part adhesive film, one typically combines all at once,a latent hardener, multi-functional epoxy resins, phenoxy resins,additives, and optionally fillers. This composition is then cast as afilm on a release layer. During the bonding process, the adhesive istransferred to one particular surface and the release layer removed.Another surface is brought into contact with the film, and the adhesivehardened or cured into a strong thermosetting adhesive through theapplication of heat and/or pressure. In this example, the two componentsof the adhesive that enable the material to cure into a thermosetadhesive are the hardener and the multi-functional epoxy. It is thelater, that sets up the cross-linked network, but it is the former thatenables this to happen. During the curing process, the latent hardenerinitiates the polymerization of the multi-functional epoxy by firstforming ring-opened adducts with the oxiranes of the epoxy resin. Onceproduced, the addition products cause a cascade of ring-opened speciesthat propagate through the adhesive, finally producing a cross-linkedthermoset material.

The active ingredient of the hardener is usually comprised of thereaction product of an amine compound, like an imidazole, and an epoxyresin. Such adducts are known to initiate and accelerate the cure ofepoxy resins (Heise, M. S.; Martin, G. C. Macromolecules, 1989, 2299-104; Heise, M. S.; Martin, G. C. J. Poly. Sci.: Part C: Polym. Lett.1988, 26, 153-157; Barton, J. M; Shepherd, P. M.; Die MakromolekularChemie 1975 176, 919-930). One drawback of these however is that theyare so effective as curatives they cannot be used directly into a 1-partadhesive because once added, they would start to kick-off the cure in arelative short period of time. What one would see therefore is a slowincrease in the viscosity of the composition, while one is attempting tomake the adhesive and its film, as the hardener continues to acceleratethe ring-opening polymerization of the epoxy moieties. This phenomenonis most commonly referred to as reduced workable lifetime, in otherwords, the time available to assemble the adhesive and make the film wasdramatically reduced because of premature hardening. Therefore, to stopthis from happening, one usually does not use amine-epoxy adductsthemselves as hardeners, but instead what is typically done is toencapsulate or coat the amine-epoxy adduct with a protective shell ofmaterial that sequesters the amine-epoxy adduct from the adhesiveenvironment. Once incorporated into the adhesive, the amine-epoxy adductis released from its protective shell through the application of heatand/or pressure. Such latent hardeners described here are commonlycalled to as a core-shell latent hardener, where the core in this caseis an amine-epoxy adduct and the shell is the protective shell.

There is one significant trade-off often encountered with core-shelllatent hardeners, which is the cure speed is often slowed and the curetemperature often increased because of the inclusion of a protectiveshell, which must be broken or rendered permeable in order to allow thecore material to be released into the adhesive environment or matrix.Without being bound by any particular theory, it is well known that asone increases the barrier properties of the shell material using suchmeans, like increasing the thickness of the shell, cross-linkingdensity, or T_(g) of the shell, or by increasing the degree ofincompatibility between the shell and the core material or the adhesivematrix, it takes more energy to release the amine-epoxy adduct into theadhesive environment. What one has therefore is a hardener that whenformulated into a 1-part adhesive has the desired property of increasedshelf life stability, but at the expense of a lower curing temperatureand a reduction of cure speed. Therefore, it continues to be a constantbalance to prepare a core-shell latent hardener that has just enough ofa protective shell to protect the core material at normal storageconditions, but not too much as to slow down the cure speed of theadhesive. Also, the release of the core material may be triggered at areasonably low temperature and completed within a narrow temperaturerange.

One of the most frequently used core-shell latent hardeners are thosecomprised of core-shell materials, as described in U.S. Pat. Nos.4,833,226, 5,219,956, US 2006/0128835, US 2007/0010636, US 2007/0055039,US 2007/0244268, EP 1,557,438, EP 1,731,545, EP 1,852, 452, and EP1,980,580. The hardeners described here are obtained, first by thesynthesis of a lump of core material, which is then pulverized intomicro-sized particles that are irregular in shape. The core material isthe reaction product of an amine compound and an epoxy resin and saidcore material functions as a hardener for epoxy compositions, such asthat found in adhesives and coatings. To improve the storage stabilityof the core material and prevent premature curing, it is encapsulatedwith a shell of a material that is impervious to components of the epoxycomposition, such as solvent, diluent, low molecular weight epoxides andadditives. To accomplish this, the pulverized solid is added to amixture of polyfunctional isocyanate, an active hydrogen compound, likewater, and an epoxy resin. The chemistry of said encapsulation procedurerelies on the cross-linking reactions and/or hydrolysis of thepolyisocyanate compound to form a cross-linked shell coating around theparticles. Typical cross-linking structures of the shell include, butare not limited to, urea, urethane, carbamate, biuret, allophanate, etc.However, the crosslinking reactions take places randomly withoutdiscrimination in the continuous phase and at the interface. It ishighly likely that some core particles are not fully encapsulated, whileunwanted byproducts such as crosslinked polyurea particles are producedin the continuous phase. Moreover, the core particles prepared by thisprocess are of irregular shape with a very broad distribution of shapeand particle size, the uniformity of the thickness and crosslinkingdensity of the shell formed thereon is very poor. As a result, theencapsulated hardener particles typically show a very broad distributionof release property and the 1-part adhesive formulated with this type ofhardener capsules often shows poor shelf-life stability and a sluggishcuring profile or a high curing temperature.

There is another group of inventions, namely EP 459,745, EP 552,976,U.S. Pat. Nos. 5,357,008, 5,480,957, 5,548,058, 5,554,714, 5,561,204,5,567,792, and 5,591,814, that also describe core shell latenthardeners, which unlike those above are spherical in shape. The corematerial is obtained as a spherical particle and is synthesized from thereaction of an amine with an active hydrogen atom (e.g., imidazole) andan epoxy resin, in an organic medium and in the presence of adispersant. The amine, epoxy resin, and dispersant are soluble in theorganic medium, while the reaction product, the core material, is not,and as a result the core particle precipitates out from solution as astable dispersion with a relatively narrow size distribution. The mostimportant factor to make a stable dispersion of desirable particle sizewith a narrow size distribution is the nature of the dispersant and theinventors show examples that use dispersants from the class of graft ofpolyacrylates, polyacrylamides, polyvinyl acetates, polyethylene oxides,polystyrenes, and polyvinyl chlorides. Once isolated, the spherical corematerial is encapsulated with an isocyanate to prepare a sphericalcore-shell latent hardener.

One disadvantage of the aforementioned latent hardeners is the need ofthe shell material to be free of defects, such as such as holes, voids,thin areas, or areas comprised of insufficient cross-link density. Thesedefects would enable the core to escape from the protective shellprematurely, either during processing or storage of the finishedarticle. Either way, this premature release of core from theencapsulated latent hardener would show up as a loss of storagestability and shelf-life (in the case of a 1-part epoxy adhesive). Thisdeficiency; however, can be overcome by the application of additionaland successive layers of the shell material over the preexisting shell,thus filling in and coating the defects with an additional layers shellmaterial.

Another limitation of the prior art is that in an attempt to make theprotective shell more impervious and thereby improving its barrierproperties, the compatibility of the shell with the surrounding epoxycomposition was neglected. The prior art teaches encapsulation in thepresence of an isocyanate, and optionally water and additional epoxy.What one then obtains is a shell comprised of a cross-linkedpolyurethane and optionally a polyurea. When formulated into an epoxyadhesive, the now hard and highly cross-linked shell could have poorcapability with the surrounding epoxy. An example of this would be amismatch of surface tensions between the surface of the shell and theepoxy; which would show up as a dewetting phenomenon in which the epoxyfails to adequately wet and spread over the surface of the shellmaterial. As a consequence therefore one would see that after curing,the adhesive would contain voids and regions of inhomogeneous curing,both of which would lead to a reduction of adhesive strength.

There remains a need for core-shell latent hardeners with improvedbarrier properties to prevent premature cure. Additionally, there is aneed of encapsulated latent hardeners with improved epoxy compatibility.

SUMMARY OF THE INVENTION

This invention relates to latent hardeners or catalysts for thermosetssuch as epoxy resins and, more particularly, to latent hardeners orcatalysts comprised of a core material that is encapsulated or coatedwith two or more shell materials. The core material, which is a curativefor epoxy resins, is further comprised of the reaction product of anamine (e.g., imidazoles, piperazines, primary aliphatic amines, andsecondary aliphatic amines) and an epoxy resin. In one embodiment, thecore material is synthesized in an organic medium and in the presence ofa dispersant which is the reaction product of carboxyl terminatedpoly(butadiene-co-acrylonitrile) (CTBN) and an epoxy resin. In oneembodiment, the reaction product of a CTBN and an epoxy resin is capableof providing a stable dispersion of spherical-shaped core particles witha narrow size distribution. In another embodiment near 100% conversionis obtained by using a slight excess of epoxy. In another embodiment,the spherical-shaped core particles are encapsulated by reacting with amulti-functional isocyanate or thioisocyanate. Optionally, an epoxyresin is added at the same time as the isocyanate to build up thethickness of the encapsulated shell. In still another embodiment, onceformed, the core material is fully encapsulated with two or more shellmaterials that are applied in a step-wise manner using amulti-functional isocyanate, or a mixture of isocyanate andmulti-functional epoxy resin, or a mixture of an isocyanate and epoxycompatible material, such as CTBN or polyacrylate modified epoxy, or amixture of an isocyanate, multi-functional epoxy, and an epoxycompatible material. Curable compositions prepared using the particleshave excellent storage stability and improved curing properties.

One aspect of this disclosure relates to an improvement to the barrierproperties and solvent resistance of a latent hardener or catalyst.

Another aspect of this disclosure relates to an improvement of barrierproperties and solvent resistance of a latent hardener or catalyst.

Another aspect of this disclosure relates to an improvement ofcompatibility of the latent hardener or catalyst with an epoxy resin orcomposition.

Another aspect of this disclosure relates to a latent hardener orcatalyst of a spherical-shape and which is fully encapsulated.

Another aspect of this disclosure relates to a latent hardener orcatalyst that releases the core material at the desired temperature,pressure, or combination of both.

Another aspect of this disclosure relates to a latent core-shell latenthardener or catalyst, wherein the hardener or catalyst is comprised of astable dispersion of spherical-shaped particles.

Another aspect of this disclosure relates to a process of makingspherical-shaped core particles using a dispersant, wherein saiddispersant is the reaction product (adduct) of a carboxyl-terminatedbutadiene-acrylonitrile rubber (CTBN) and an epoxy resin.

Another aspect of this disclosure relates to a curing agent comprised ofan amine compound, an epoxy resin, and a dispersant, wherein saiddispersant is the adduct of CTBN and an epoxy resin.

Another aspect of this disclosure relates to a process for making thecuring agent.

Another aspect of this disclosure relates to a masterbatch that iscomprised of the curing agent.

Another aspect of this disclosure relates to an electronic device or aflat panel display comprising the composition that is comprised of thecuring agent disclosed herein. For example a common method that is usedto connect the driver integrated circuit (IC) to the electronic deviceor flat panel display is through the use of either a chip-on-glass (COG)or chip-on-film (COF). In the constructions of the COG and COF,anisotropic conducing film adhesives (ACF) and non-conducting filmadhesives (NCF) are typically used to attach the COG or COF to thedriver IC and it is the curing agent that enables the adhesives to cureand produce a permanent bond between the components. Accordingly, in oneembodiment, the integrated circuit chip or other electronic component isattached using an epoxy adhesive containing the curing agent describedherein.

Another aspect of this disclosure relates to a composition containingthe curing agent, where the composition is an adhesive, conductingadhesive, composite, molding compound, anisotropic conducting film (ACF)adhesive, non-random array ACF, non-conductive adhesive film (NCF),coating, encapsulant, underfill material, lead or free solder.

Another aspect of this disclosure relates to a circuit board comprisingan epoxy adhesive composition comprised of the curing agent that isdisclosed herein. Traditionally, the electronic components, such asresistor, capacitor, and IC are assembled to the circuit board through asoldering process. This process requires high temperature and generateswaste. However, an ACF, NCF or conductive adhesive containing thedisclosed curing agent provides an alternative method to mount theelectronic components on the circuit board without the use to hightemperatures, waste, and toxic heavy metals. In this application, ACFand NCF provide the electrical contact and secure the component to theboard.

Another aspect of this disclosure relates to an electronic device ordisplay which is assembled using an epoxy adhesive composition thatcontains the curing agent disclosed herein.

Another aspect of this disclosure relates to a flip chip comprising theadhesive composition containing the curing agent disclosed herein.Traditionally a flip chip is a chip that mounted to the substrate in twosteps. First, the chip is bonded to the substrate through soldering oreutectic bonding. Underfill material, typically in liquid form, is thenfilled in the gap and cured between the chip and the substrate.Replacing the soldering or eutectic bonding process with an ACF or NCFcontaining the disclosed curing agent is an alternative method toaccomplish the first step. Not only does the adhesive approach providedadvantages encountered with circuit boards, but the ACF and NCF alsofunction as the underfill material to fill the gap between the chip andthe substrate thereby accomplishing the process in a single step, wheretwo were used before.

Another aspect of this disclosure relates to an electronic device ordisplay where the composition is cured, partially cured, or un-cured andis comprised of the curing agent.

Another aspect of this disclosure relates to a semiconductor device,such as a high definition LCD, Electronic Paper (ePaper), miniprojectors, and cell phones that are comprised of flat panel displays,electronic devices, circuit boards, and flip chips in which an epoxyadhesive containing the curing agent disclosed herein is used asdescribed above.

Another aspect of this disclosure is a fixed array ACF, where the fixedarray ACF is an ACF wherein the gold particles are dispersed in theadhesive film in a predetermined pattern, such as that described inTrillion's patent application 2006/0280912 A1 wherein an epoxy adhesivecontaining the curing agent disclosed herein is used to construct thearray.

Another aspect of this disclosure is a High T_(g) 1-part moldingcompound comprising a protected phenolic compound as described inpending U.S. application Ser. No. 12/008,375 filed Jan. 10, 2008 whichis herein incorporated by reference, where the protected phenoliccompound comprises an aryl glycidyl carbonate moiety, and the curingagent disclosed herein.

Still another aspect of this disclosure are 1-part composites, includingprepreg composites and molding compounds, such as sheet moldingcompounds (SMC), bulk molding compounds (BMC), and dough moldingcompounds (DMC) wherein the curing agent is the curing agent disclosedherein.

Still another aspect of the disclosure is adhesives and coatingapplications, including solder mask and impregnation coatings in whichthe curing agent is the curing agent disclosed herein.

Another aspect of this disclosure employs epoxy resins containing thecuring agent disclosed herein in assembly and packaging forsemi-conductor applications such as described in Colclaser, Roy A.;“Microelectronics Processing and Device Design”; John Wiley & Sons,Publishers: New York, 1980; Chapter 8, page pp. 163-181.

Another aspect of this disclosure relates to the circuit board where thecomposition is cured, partially cured, or un-cured and is comprised ofthe curing agent disclosed herein.

Another aspect of this disclosure relates to a flip chip where the epoxyadhesive composition described herein is cured, partially cured, orun-cured and is comprised of the curing agent.

Another aspect of this disclosure relates to a semiconductor devicecomprising the composition containing the curing agent. Another aspectof this disclosure relates to a semiconductor device where thecomposition is cured, partially cured, or un-cured and is comprised ofthe curing agent.

Another aspect of this disclosure relates to a composition, where thecomposition is a 1-part adhesive composition having a substantially longshelf-life at storage conditions and the composition is reactive ateither the curing temperature or the molding temperature, and thecomposition contains the curing agent disclosed herein.

Another aspect of this disclosure relates to a composition containingthe curing agent, where after cure the composition shows adhesion atinterfaces, low shrinkage on cure, and low coefficient of thermalexpansion (CTE).

Another aspect of this disclosure relates to a composition containingthe curing agent, where the composition is a matrix for a compositematerial or molding compound.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing showing a core material encapsulated with twoprotective shell materials. In the case for improved latent hardenercompatibility the composition of protective shell 2 is selected suchthat is comprised of an epoxy compatible material, while the compositionof shell 1 is selected based only on its barrier properties.

FIG. 2 is an electron micrograph of core particles of spherical shapecomprised of 2-methylimidazole, diglycidyl ether of bisphenol A (DGEBA),and the CTBN-epoxy adduct isolated from CVC Thermoset Materials HyPox™RK84.

FIG. 3 is an electron micrograph of core particles of spherical shapecomprised of 2-methylimidazole, diglycidyl ether of bisphenol A (DGEBA),and the CTBN-epoxy adduct isolated from CVC Thermoset Materials HyPox™RK84, wherein the core particle is encapsulated with4,4′-methylenebis(phenyl isocyanate) (MDI).

FIG. 4 is an electron micrograph of a single core particle of sphericalshape comprised of 2-methylimidazole, diglycidyl ether of bisphenol A(DGEBA), and the CTBN-epoxy adduct isolated from CVC Thermoset MaterialsHyPox™ RK84.

FIG. 5 is the chemical structure of a CTBN-epoxy adduct (c) where ahydroxyl-functional epoxy resin (b) such as that of CVC ThermosetSpecialties HyPox RK84 is used in the synthesis along with CTBN (a). Theresidual unreacted epoxy resin (b) is removed prior to (c) being used asa dispersant.

FIG. 6 is the chemical structure of a CTBN-epoxy adduct (e) wheredisglydicyl ether of bisphenol A (d) such as that of CVC ThermosetSpecialties HyPox RA1340 is used in the synthesis, along with CTBN (a).

DETAILED DESCRIPTION OF THE INVENTION

In accordance with one embodiment, the curing agent is an adduct of: (i)an amine, (ii) an epoxy compound, and (iii) an adduct of an elastomerand an epoxy resin. The elastomer/epoxy resin adduct functions as anreactive dispersant enabling the formation of a dispersion of sphericalun-encapsulated particles in the reaction medium.

Another aspect of the invention is a method for the preparation of finespherical core particles of a curing agent that comprises reacting anamine compound with an epoxy/elastomer adduct followed by an epoxycompound, in the presence of a continuous phase at elevated temperatureswith agitation, and recovering fine spherical particles formed from thereaction mixture solution. Optionally, the recovered particles may befiltered to remove aggregated particles and classified by methods suchas gravity fractionation, filtration, sedimentation, field flowfractionation, and field flow classification to remove small satelliteparticles. The continuous phase is an organic solvent or solvent mixturecomprised of either a solvent capable of dissolving the amine compound,the epoxy compound and the epoxy/elastomer adduct but incapable ofdissolving the adduct formed from the three reactants or a mixture of asolvent and non-solvent, where the solvent is capable of dissolving theamine compound, the epoxy compound and the epoxy/elastomer adduct butincapable of dissolving the adduct particles formed from the threereactants or a mixture and the non-solvent is a non-solvent for theamine compound, the epoxy compound, the epoxy/elastomer adduct, and theadduct particles formed from the three reactants. The selection of thecontinuous phase affects the dispersion stability and the particle sizeand particle size distribution.

Yet another embodiment of the invention is a heat curable compositionthat comprises, as its major components, an epoxy composition andspherical particles of the curing agent. In this case, the sphericalparticles of the curing agent of this invention are not soluble orswellable in the epoxy composition. In one embodiment the particles havea melting flow temperature of at least about 50° C. and a particlediameter of 0.1 μm to 30 μm. The particles are incorporated in theadhesive in an amount of about 1 to 60 parts by weight per 100 parts byweight of the epoxy resin.

The present invention also includes a curing agent masterbatch for epoxyresins wherein the masterbatch comprises a liquid epoxy resin in whichfine spherical particles of the curing agent are uniformly dispersed. Ina particular embodiment, the particles have been reacted with 1 to 100parts by weight of a polyfunctional isocyanate compound, and optionallywith 1-100 parts by weight of an epoxy compound, based on 100 parts byweight of said particles. The particles are then allowed to react one ormore additional times in successive steps with 1 to 100 parts by weightof a polyfunctional isocyanate compound, and optionally with 1-100 partsby weight of a multifunctional epoxy compound, and optionally with 1-100parts by weight of an epoxy compatible material, based on 100 parts byweight of said particles.

The present invention further includes a method for preparation of acuring agent masterbatch for epoxy resin with comprises the step ofdispersing spherical particles of the curing agent in an epoxy resin ata temperature below the melt flow temperature of said sphericalparticles.

Curing Agent Epoxy Plus Amine Compound

In the present invention the amine compounds and the epoxy compoundswhich can be employed in the preparation of the curing agent areselected based on its chemical structure which promotes the curingreaction by anionic polymerization, its melting point, and itscompatibility with the epoxy resin which will be cured in a molten orplasticized viscoelastic state, its quick curability and its reactivity.The melting flow temperature is defined herein as the temperature atwhich the substance begins to flow as a molten fluid, as determined bythe conventional methods. Examples of amine and epoxy compounds usefulin certain embodiments of the invention are disclosed in EP 459,745, EP552,976, U.S. Pat. Nos. 5,357,008 , 5,480,957, 5,548,058, 5,554,714,5,561,204, 5,567,792, and 5,591,814, which are incorporated herein byreference.

Amine Compound

While any amine compound can be used, the selection of the amine will bebased upon the nature of the epoxy compound. An amine is selected thatreacts with the epoxy compound but enables the reaction without fullpolymerization. While it is possible to use substantially any aminecompounds when reacting monofunctional epoxy compounds, when reactingpolyfunctional epoxy compounds, an amine compound which has only oneactive hydrogen, i.e., a secondary amino group that contributes to thereaction of the epoxy group. Use of compounds having a tertiary aminogroup, i.e., having no active hydrogen, is also permitted. The followingcompounds are illustrative examples of amine compounds which can becombined with bifunctional bisphenol A diglycidyl ether: imidazolesrepresented by 2-methylimidazole and 2,4-dimethylimidazole, piperazinesrepresented by N-methyl piperazine and N-hydroxylethyl-piperazine,anabasines represented by anabasine, pyrazoles represented by3,5-dimethyl-pyrazole, purines represented by tetra-methyl-quanidine orpurine, pyrazoles represented by pyrazole, and triazoles represented by1,2,3-triazole, and the like.

Epoxy Compound

Examples of epoxy compounds are monofunctional epoxy compounds such asn-butyl glycidyl ether, styrene oxide and phenylglycidyl ether;bifunctional epoxy compounds such as bisphenol A diglycidyl ether,bisphenol F diglycidyl ether, bisphenol S diglycidyl ether anddiglycidyl phthalate; trifunctional compounds such as triglycidylisocyanurate, triglycidyl p-aminophenol; tetrafunctional compounds suchas tetraglycidyl m-xylene diamine andtetraglycidyldiaminodiphenylmethane; and compounds having morefunctional groups such as cresol novolac polyglycidyl ether, phenolnovolac polyglycidyl ether and so on. The selection of epoxy is alsodetermined by the type of the amine compound to be combined. The epoxycompounds are also selected based upon the softening point of the adductformed and the compatibility in a molten state with respect to the epoxyresin which is to be cured. Since the majority of the epoxy resins to becured comprise bisphenol A diglycidyl ether, this compound is mosttypically used as the starting material for the preparation of anadduct. In one embodiment, epoxy compounds having an epoxy equivalentweight of, at most about 1,000, and preferably at most about 500 aretypically employed.

Solvent

It is also important to select a solvent system which can dissolve theamine compounds and the epoxy compound as the starting materials but canprecipitate the adduct in the form of particles without dissolution.Examples of solvents that can be used in certain embodiments of thepresent invention are methyl isobutyl ketone, methyl isopropyl ketone,methyl ethyl ketone, acetone, n-butylacetate, isobutyl acetate, ethylacetate, methyl acetate, tetrahydrofuran, 1,4-dioxane, cellosolve,ethyleneglycol monoethyl ether, diethyleneglycol dimethyl ether,anisole, toluene, p-xylene, benzene, methylene chloride, chloroform,trichloroethylene, chlorobenzene and pyridine. These solvents can beused alone, or two or more solvents can be used together.

Non-Solvent

Additionally a non-solvent may need to be added to assist with forcingthe amine compound to react with the epoxy functionalities of thedispersion stabilizer and epoxy resin. A non-solvent in the case is anysolvent that does not dissolve either the amine compound, dispersionstabilizer, or epoxy resin. One possible class of compounds that can beused as non-solvents are linear or branched aliphatic compounds such asheptane, hexane, octane, iso-octane, petroleum ether, and the like. Oneexample of a non-solvent in combination with a solvent is a mixture ofheptane and MIBK. In addition to the above-mentioned solvent andnon-solvent, a diluent or a weak solvent may be optionally used to widenthe formulation or process window.

Dispersion Stabilizer or Dispersant

The dispersion stabilizer or dispersant enables a stable dispersion ofthe adduct particles in the reaction medium. Without such a dispersionstabilizer, the particles of the adduct formed may aggregate andprecipitate out as a viscous mass during the reaction, and thus thedesired fine spherical particles cannot be obtained. An optimumdispersant is important for the preparation of a stable dispersion witha narrow particle size distribution. Reactive dispersants are often moreeffective than non-reactive dispersants since desorption or migration ofthe dispersant away from the particle surface is less likely once itreacts with the particle phase. Elastomer/epoxy adducts are used asreactive dispersants in accordance to this invention. A suitablemolecular weight range of the reactive dispersant is from about 1,000 to300,000, preferably from about 2,000 to 100,000, and most preferablyfrom about 3,000 to 10,000.

Epoxy/Elastomer Adducts as Reactive Dispersants

The epoxy/elastomer adduct itself generally includes about 1:5 to 5:1parts of epoxy or other polymer to elastomer, and more preferably about1:3 to 3:1 parts of epoxy to elastomer. More typically, the adductincludes at least about 5%, more typically at least about 12% and evenmore typically at least about 18% elastomer and also typically includesnot greater than about 50%, even more typically no greater than about40% and still more typically no greater than about 35% elastomer,although higher or lower percentages are possible. The elastomersuitable for the adduct may be functionalized at either the main chainor the side chain. Suitable functional groups include, but are notlimited to, —COOH, —NH₂′—NH—, —OH, —SH, —CONH₂, —CONH—, —NHCONH—, —NCO,—NCS, and oxirane or glycidyl group, etc. The elastomer optionally maybe vulcanize-able or post-crosslink-able. Exemplary elastomers include,without limitation, natural rubber, styrene-butadiene rubber,polyisoprene, polyisobutylene, polybutadiene, isoprene-butadienecopolymer, neoprene, nitrile rubber, butadiene-acrylonitrile copolymer,butyl rubber, polysulfide elastomer, acrylic elastomer, acrylonitrileelastomers, silicone rubber, polysiloxanes, polyester rubber,diisocyanate-linked condensation elastomer, EPDM (ethylene-propylenediene rubbers), chlorosulphonated polyethylene, fluorinatedhydrocarbons, thermoplastic elastomers such as (AB) and (ABA) type ofblock copolymers of styrene and butadiene or isoprene, and (AB)n type ofmulti-segment block copolymers of polyurethane or polyester, and thelike. In the case that carboxyl-terminated butadiene-acrylonitrile(CTBN) is used as the functionalized elastomer, the preferable nitrilecontent is from 12-35% by weight, more preferably from 20-33% by weight.

An example of a preferred epoxide-functionalized epoxy/elastomer adductis sold in admixture with an epoxy resin under the trade name HyPox™RK84 (FIG. 5), a bisphenol A epoxy resin modified with CTBN elastomer,and the trade name HyPox™ RA1340 (FIG. 6), an epoxy phenol novolac resinmodified with CTBN elastomer, both commercially available from CVCThermoset Specialties, Moorestown, N.J. In addition to bisphenol A epoxyresins, other epoxy resins can be used to prepare the epoxy/elastomeradduct, such as n-butyl glycidyl ether, styrene oxide and phenylglycidylether; bifunctional epoxy compounds such as bisphenol A diglycidylether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether anddiglycidyl phthalate; trifunctional compounds such as triglycidylisocyanurate, triglycidyl p-aminophenol; tetrafunctional compounds suchas tetraglycidyl m-xylene diamine andtetraglycidyldiaminodiphenylmethane; and compounds having morefunctional groups such as cresol novolac polyglycidyl ether, phenolnovolac polyglycidyl ether and so on. Examples of additional oralternative epoxy/elastomer and other adducts suitable for use in thepresent invention are disclosed in U.S. Pat. No. 6,846,559 and U.S.Patent Publication 2004/0204551 to Czaplicki, Michael both of which areincorporated herein by reference.

Amine Compound Plus Reactive Dispersant

To prepare the curing agent, in one non-limiting process, the selectedamine compound and the epoxide-functionalized reactive dispersant arefirst allowed to react to ensure the dispersant is fully incorporated.The reactive dispersant is dissolved in a selected solvent system andallowed to react using a combination of heating and stirring from about2 min to about 3 h, preferably from about 4 min to about 2 h, and mostpreferably from about 5 min to about 1 h. Thus, the reaction temperaturewhich can be employed in the present invention is typically 40° C. to90° C., preferably 50° C. to 80° C., and the concentration of thestarting materials, i.e. the amine compound and theepoxide-functionalized reactive dispersant, is typically about 2 to 40%by weight, preferably about 5 to 30% by weight. The amount of reactivedispersant is from about 1 to 70% (w/w) based on the combined weights ofthe reactive dispersant and amine compound, preferably from about 5 to50% (w/w) based on the combined weights of the reactive dispersant andamine compound and most preferably from about 9 to 35% (w/w) based onthe combined weights of the reactive dispersant and amine compound. Inthe special case where the epoxide-functionalized reactive dispersantcontains a residual epoxy compound that is not bonded to the elastomer,such as in FIGS. 5 and 6, an additional purification step is undertakenwhich consists of removing the unreacted epoxy compound from saidreactive dispersant. This purification step is especially important toavoid the formation of aggregates and lumps of solid material after theaddition of the epoxy compound (see below).

Epoxy Compatible Material

The epoxy compatible material is any epoxy-functional material thatcontains a functional group or groups that are compatible with an epoxyresin. One example are the epoxide-functionalized epoxy/elastomeradducts that are sold as admixtures with an epoxy resin, availablecommercially under the trade name HyPox™ RK84 (FIG. 5) and the tradename HyPox RA1340 (FIG. 6), from CVC Thermoset Specialties, Moorestown,N.J. Said HyPox elastomers contain the epoxy compatibilizing monomeracrylonitrile. Other examples would include, but are not limited to,epoxy-functional polyacrylates that would contain epoxy compatibleco-monomers, like acrylonitrile and methyl methacrylate.

Amine Compound Plus Epoxide-Functionalized Reactive Dispersant PlusEpoxy Compound, Formation of the Un-Encapsulated Particles.

After the amine compound has been allowed to react with theepoxide-functionalized dispersant, the formation of the un-encapsulatedlatent hardener particles begins with the addition of the epoxycompound. A solution of the epoxy compound is slowly added to thestirred heated solution of the amine compound-dispersion stabilizersolution over the course from about 5 min to 6 h, preferably from about10 min to 4 h, and most preferably from about 15 min to 2 h, using anapparatus that allows for a constant uninterrupted addition of epoxyresin solution, such as a syringe pump or peristaltic pump or the like.The amount of epoxy compound is from about 10 to 90% (w/w) based on thecombined weights of the amine compound, reactive dispersant, and epoxycompound, preferably from about 30 to 85% (w/w) based on the combinedweights of the amine compound, reactive dispersant, and epoxy compound,and most preferably from about 50 to 80% (w/w) based on the combinedweights of the amine compound, reactive dispersant, and epoxy compound.In one example, a solution of the reactive dispersant and the amine isagitated, while heating, under an inert atmosphere and after apredetermined time, a solution of epoxy compound is added over apredetermined time. The originally clear solution will become opaque asthe epoxy compound begins to react. As the reaction progresses, theopaqueness of the reaction system gradually increases, with acharacteristic milky white turbid dispersion eventually occurring.

When the reaction temperature and the concentration of the startingmaterials are too high, aggregates may easily form even in the presenceof a suitable amount of the reactive dispersant. Thus, the reactiontemperature which can be employed in the present invention is typically40° C. to 90° C., preferably 50° C. to 80° C., and the concentration ofthe starting materials, i.e. the amine compound, the reactivedispersant, and epoxy compound, is typically 2 to 40% by weight,preferably 5 to 30% by weight. Generally, the particle size of theadduct increases with increased concentrations of the starting materialsbut decreases with increased concentrations of the reactive dispersant.

Encapsulation

The particles are subsequently encapsulated, with each layer ofencapsulate or protective shell applied over the particle in two or moresuccessive steps. Various known methods for encapsulating sphericalcuring agents may be used in this invention. In one embodiment, theadduct particles may be reacted with an encapsulation agent to form twoor more protective shells, where said encapsulating agent is comprisedof a polyfunctional isocyanate compound or a mixture of polyfunctionalisocyanate compounds and multifunctional epoxy compounds or a mixture ofpolyfunctional isocyanate and epoxy compatible compound (e.g.,acrylonitrile), or a mixture of a polyfunctional isocyanate, epoxycompounds, and epoxy compatible compound. Suitable polyfunctionalisocyanate compounds include the mononuclear and polynuclear species oftoluene diisocyanate, methylene diphenyl diisocyanate, hydrogenatedmethylene diphenyl diisocyanate, 1,5-naphthalene diisocyanate,isophorone diisocyanate, hexamethylene diisocyanate, xylylenediisocyanate, hydrogenated xylylene diisocyanate, tetramethylxylenediisocyanate, 1,3,6-hexamethylene triisocyanate, lysine diisocyanate,triphenylethane triisocyanate, polyfunctional isocyanate compoundsformed by addition of such compounds and other activehydrogen-containing compound, and any mixtures thereof.

Representative examples of multifunctional epoxies include methylenebisglycidyl aniline, HELOXY™ Modifier 48 (a product of Hexion SpecialtyChemicals), Toagosei GP-301 graft polymethylmethacrylate-g-epoxymodified acrylate polymer, and a multi-functional epoxy containingacrylonitrile (epoxy compatible co-monomer) but other multifunctionalepoxies should also work.

The amount of the encapsulation agent employed to encapsulate theun-encapsulated particles affects the storage stability and thecurability of a curing agent masterbatch. With the same particles of theaddition product, increased amounts of the encapsulation agent improvethe storage stability, but lower the curability. Thus, for adductparticles having a diameter of about 0.1 micron to 30 micron, theencapsulation agent is employed in ratio from about 50:50 to 95:5 (w/w)core particles to encapsulation agent, preferably from about 60:40 to90:10 (w/w) core particles to encapsulation agent, and most preferablyin a ratio from about 70:30 to 90:10 (w/w) core particles toencapsulation agent. Additionally, when the encapsulation agent is amixture of isocyanate compounds and epoxy compounds or isocyanatecompounds and epoxy compatible compounds, the amount of epoxy compoundis used in a ratio from about 1:99 to 99:1 (w/w) isocyanate compounds toepoxy compounds, preferably from about 60:40 to 99:1 (w/w) isocyanatecompounds to epoxy compounds, and most preferably in a ratio from about80:20 and 99:1 (w/w) isocyanate compounds to epoxy compounds.Additionally, when the encapsulation agent is a mixture of isocyanatecompounds, epoxy compounds, and epoxy compatible compounds, the amountof epoxy compound is used in a ratio from about 1:99 to 99:1 (w/w)isocyanate compounds to epoxy compounds, preferably from about 60:40 to99:1 (w/w) isocyanate compounds to epoxy compounds plus epoxy compatiblecompounds, and most preferably in a ratio from about 80:20 and 99:1(w/w) isocyanate compounds to epoxy compounds. Thus, the compromisebetween storage stability and curability varies depending on the size ofthe adduct particle, with smaller particle sizes requiring increasedamounts of shell forming material such as polyfunctional isocyanate toachieve the same release or barrier properties.

In one embodiment, when the particle forming reaction is completed, theun-encapsulated particles are isolated from the reaction medium byfiltration and then washed with fresh solvent. The particles are thensubsequently encapsulated.

Masterbatch

In general, to form the masterbatch, the encapsulated particles areuniformly dispersed in an epoxy resin in a range from about 5 to 90%(w/w) based on the combined weights of the particles and epoxy resin,preferably in the range of about 15 to 80% (w/w) based on the combinedweights of the particles and liquid epoxy compound, and most preferablyin the range of about 20 to 70% (w/w) based on the combined weights ofthe particles and liquid epoxy compound.

In one embodiment, the epoxy resin can be one or more epoxy resins ofbisphenol A, bisphenol F, novolac epoxies, and the like.

In one embodiment, to avoid the formation of secondary particles, theencapsulated particles are mechanically dispersed in the epoxy resin asprimary particles, for example, by blending with a three roll mill.

In another embodiment, after the encapsulation process is completed,heating and stirring are stopped and an epoxy resin is added to thedispersion. The mixture is again stirred, enough to distribute the epoxyresin equally in the dispersion. The solvent is then removed, usingvacuum distillation, or the like, such that the total solid content isabout 60 to 100% (w/w), preferably about 70 to 100% (w/w), and mostpreferably about 80 to 100% (w/w). The particles are then dispersedfurther in the epoxy resin using techniques known to those of ordinaryskill in the art, such as a three-roll mill, or the like.

In yet another embodiment, when the reaction is completed, the solventis removed using vacuum distillation to 100% (w/w) solids content. Thesolid particles are then added to an epoxy resin and the particlesdispersed further in epoxy resin using techniques known to those ofordinary skill in the art, such as a three-roll mill, or the like.

In still yet another embodiment, when the reaction is completed, theparticles are separated by filtering the dispersion of the particles.Fresh solvent is used to wash off unreacted starting material adhered tothe surface of the particles. An epoxy resin is then added to the solidparticles and the mixture dispersed further using techniques known tothose of ordinary skill in the art, such as a three-roll mill, or thelike.

The adhesive compositions disclosed herein are potentially useful invarious applications including in a conducting adhesive, composite,molding compound, anisotropic conducting film (ACF) adhesive, non-randomarray ACF, non-conductive adhesive film (NCF), coating, encapsulant,underfill material, lead-free solder, etc.

Having described the invention in detail, the invention will beillustrated by the following non-limiting examples:

EXAMPLES Examples for the Formation of the Un-Encapsulated CoreParticles Example 1 Synthesis of Un-Encapsulated Core Particles from2-methylimidazole, DGEBA, and HyPox™ RK 84 (1)

Commercial material HyPox RK84 [a commercial material of CVC ThermosetSpecialties and mixture of a bisphenol A epoxy resin and its adduct withCTBN (FIG. 5)] was used as the dispersion stabilizer. A three-neckedround bottom flask, equipped with a PTFE fluoropolymer half moon-shapedoverhead stirrer, a reflux condenser, an addition funnel, and an argongas inlet was charged with 0.93 g of the CTBN-epoxy adduct, 1.64 g (0.02mole) of 2-methylimidazole and 48 g of 4-methyl-2-pentanone (MIBK). Thereactor was placed in an 80° C. bath and purged with argon. After 1 h, asolution of 3.39 g (0.019 equivalent weight) DER™ 332 (a product of DowChemical) and 3.4 g of MIBK was added dropwise over the course of 20min, after which the reaction was allowed to stir at 300 rpm for 6 hrunder an argon atmosphere. A white milky dispersion was formed. Thedispersion was discharged from the reactor, centrifuged, washed withMIBK, and evaporated to dryness to afford 3.6 g (60.4% yield) ofproduct. A small drop of the dispersion was diluted, coated on glassslide and dried in vacuum at room temperature. The dried sample wassputtered with a thin layer of gold and the scanning electron micrographof this taken using a Hitachi S-2460N scanning electron microscope.

Example 2 Synthesis of Un-Encapsulated Core Particles from2-methylimidazole, DGEBA, and HyPox™ RK 84 (2)

A CTBN-epoxy adduct that was isolated from CVC Thermoset SpecialtiesHyPox™ RK84 was used as the dispersion stabilizer. The adduct wasobtained by dissolving the material in methyl ethyl ketone, followed byprecipitation with methanol, and repeating the process two more times.The un-encapsulated core particles 2 were synthesized from 0.51 g of theCTBN-epoxy adduct, 1.63 g (0.02 mole) of 2-methylimidazole, 3.51 g (0.02equivalent weight) DER™ 332 and 51 g of MIBK using the procedure ofExample 1 to afford 4.4 g (78% yield) of particles.

Example 3 Synthesis of Un-Encapsulated Core Particles from2-methylimidazole, DGEBA, and HyPox™ RA 1340 (3)

Commercial material HyPox RA1340 [a commercial material of CVC ThermosetSpecialties and mixture of diglycidyl ether of bisphenol A and itsadduct with CTBN (FIG. 6)] was used as the dispersion stabilizer. Themicrocapsule core 3 was synthesized from 1.15 g of the aforementionedCTBN-epoxy adduct, 1.64 g (0.02 mole) of 2-methylimidazole, 2.87 g(0.0164 equivalent weight) DER™ 332 and 51 g of MIBK using the procedureof Example 1 to afford 1.2 g (21.2% yield) of particles.

Example 4 Synthesis of Un-Encapsulated Core Particles from2-methylimidazole, DGEBA, and HyPox™ RA 1340 (4)

A CTBN-epoxy adduct isolated from CVC Thermoset Specialties HyPox™ RA1340 was used as the dispersion stabilizer. The adduct was obtained byfirst dissolving the material in methyl ethyl ketone, followed byprecipitation with methanol, and repeating the process two more times.The un-encapsulated core particles 4 were synthesized from 0.53 g of theCTBN-adduct, 1.65 g (0.02 mole) of 2-methylimidazole, 3.5 g (0.02equivalent weight) DER™ 332, and 51 g of MIBK using the procedure asdescribed in Example 1 to afford 2.6 g (45.9% yield) of particles.

Example 5 Synthesis of Un-Encapsulated Core Particles from2-ethyl-4-methylimidazole, DGEBA, and HyPox™ RK 84 (5)

The un-encapsulated core particles 5 were synthesized from 0.57 g of theCTBN-epoxy adduct of Example 2, 2.20 g (0.02 mole) of2-ethyl-4-methylimidazole, 3.5 g (0.02 equivalent weight) DER™ 332, and63 g of MIBK using the procedure of Example 1 to afford 0.7 g (11.2%yield) of particles.

Example 6 Synthesis of Un-Encapsulated Core Particles from2-methylimidazole, DGEBA, and HyPox™ RA 1340 (6)

The un-encapsulated core particles 6 were synthesized from 0.26 g of theCTBN-epoxy adduct of Example 4, 1.64 g (0.02 mole) of 2-methylimidazole,3.5 g (0.02 equivalent weight) DER™ 332, and 50 g of MIBK using theprocedure of Example 1 to afford 1.6 g (26.9% yield) of particles.

Example 7 Synthesis of Un-Encapsulated Core Particles from2-ethyl-4-methylimidazole, DGEBA, and HyPox™ RK 84 (7)

The un-encapsulated core particles 7 were synthesized from 0.57 g of theCTBN-epoxy adduct of Example 2, 2.20 g (0.02 mole) of2-ethyl-4-methylimidazole, 3.5 g (0.02 equivalent weight) DER™ 332 and56 g of MIBK using the procedure of Example 1 and the reaction wasallowed to stir at 300 rpm for 16.5 h under an argon atmosphere toafford 2.5 g (40% yield) of particles.

Example 8 Synthesis of Un-Encapsulated Core Particles from2-methylimidazole, DGEBA, and HyPox™ RK 84 (8)

The microcapsule core 8 was synthesized from 0.52 g of the CTBN-epoxyadduct of Example 2, 1.64 g (0.02 mole) of 2-methylimidazole, 3.5 g(0.02 equivalent weight) DER™ 332, and 51 g of MIBK using the procedureof Example 1. The reaction was allowed to stir at 300 rpm for 16 h underan argon atmosphere to afford 4.0 g (71% yield) of particles.

Example 9 Synthesis of Un-Encapsulated Core Particles from2-methylimidazole, DGEBA, and HyPox™ RK 84 (9)

The un-encapsulated core particles 9 were synthesized from 0.52 g of theCTBN-epoxy adduct of Example 2, 1.64 g (0.02 mole) of 2-methylimidazole,3.5 g (0.02 equivalent weight) DER™ 332, and 52 g of MIBK using theprocedure of Example 1. The reaction was allowed to stir at 1000 rpm for6 h under an argon atmosphere to afford 4.18 g (74% yield) of particles.

Example 10 Synthesis of Un-Encapsulated Core Particles from2-methylimidazole, DGEBA, and HyPox™ RK 84 (10)

The un-encapsulated core particles 10 were synthesized from 0.52 g ofthe CTBN-epoxy adduct of Example 2, 1.64 g (0.02 mole) of2-methylimidazole and 37.3 g of 4-methyl-2-pentanone (MIBK). The reactorwas placed in an 80° C. bath and purged with argon. After 1 h, asolution of 3.5 g (0.02 equivalent weight) DER™ 332 (a product of DowChemical) and 3.5 g of MIBK was added dropwise over the course of 15min, after which the reaction was allowed to stir at 1000 rpm for 1 hunder an argon atmosphere. After this, 10 g of heptane was addeddropwise over the course of 1 h. The reaction was allowed to stir at1000 rpm for another 4 h. A white milky dispersion was formed. Thedispersion was discharged, centrifuged, washed with MIBK, and evaporatedto dryness to afford 2.1 g (37% yield) of dried particles.

Example 11 Synthesis of Un-Encapsulated Core Particles from2-methylimidazole, DGEBA, and HyPox™ RK 84 (11)

The un-encapsulated core particles 11 were synthesized from 0.52 g ofthe CTBN-epoxy adduct of Example 2, 1.64 g (0.02 mole) of2-methylimidazole, and 37.3 g of 4-methyl-2-pentanone (MIBK). Thereactor was placed in an 80° C. bath and purged with argon. After 1 h, asolution of 3.5 g (0.02 equivalent weight) DER™ 332 (a product of DowChemical) and 3.5 g of MIBK was added dropwise over the course of 15min, after which the reaction was allowed to stir at 1000 rpm for 1 hunder an argon atmosphere, after which 3 g of heptane was added dropwise over the course of 1 h. The reaction was allowed to stir at 1000rpm for 4 h. A white milky dispersion was formed. The dispersion wasdischarged, centrifuged, washed with MIBK, and evaporated to dryness toafford 3.0 g (53% yield) of dried particles.

Example 12 Synthesis of Un-Encapsulated Core Particles from2-methylimidazole, DGEBA, and HyPox™ RK 84 (12)

The un-encapsulated core particles 12 were synthesized from 1.05 g ofthe CTBN-epoxy adduct of Example 2, 1.64 g (0.02 mole) of2-methylimidazole, 3.5 g (0.02 equivalent weight) DER™ 332, and 51 g ofMIBK using the procedure of Example 1. The reaction was allowed to stirat 1000 rpm for 6 h to afford 4.4 g (71% yield) of particles.

Example 13 Synthesis of Un-Encapsulated Core Particles from2-methylimidazole, DGEBA, and HyPox™ RK 84 (13)

A three-necked round bottom flask, equipped with a PTFE fluoropolymerhalf moon-shaped overhead stirrer, a reflux condenser, an additionfunnel, and an argon gas inlet. The flask was charged with 0.52 g of theCTBN-epoxy adduct of Example 2, 1.64 g (0.02 mole) of 2-methylimidazole,5.1 g of heptane and 42.3 g of 4-methyl-2-pentanone (MIBK). The reactionflask was placed in an 80° C. bath and purged with argon. After 1 h, asolution of 3.5 g (0.02 equivalent weight) DER™ 332 (a product of DowChemical) and 3.6 g of MIBK was added dropwise over the course of 15min, after which the reaction was allowed to stir at 1000 rpm for 6 h. Awhite milky dispersion was formed. The dispersion was discharged,centrifuged, washed with MIBK, and evaporated to dryness to afford 3.4 g(60% yield) of particles.

Example 14 Synthesis of Un-Encapsulated Core Particles from2-methylimidazole, DGEBA, and “Purified” HyPox™ RK 84 (14)

A three-necked round bottom flask, equipped with a PTFE fluoropolymerhalf moon-shaped overhead stirrer, a reflux condenser, an additionfunnel, and an argon gas inlet was charged with 0.52 g of the CTBN-epoxyadduct of Example 2, 1.64 g (0.02 mole) of 2-methylimidazole, 5.1 g ofheptane and 46.8 g of 4-methyl-2-pentanone (MIBK). The reactor wasplaced in an 80° C. bath and purged with argon and stirred for 1 h at300 rpm. A solution of 3.5 g (0.02 equivalent weight) DER™ 332 (aproduct of Dow Chemical) and 3.5 g of MIBK was added dropwise over thecourse of 15 min, after which the reaction was allowed to stir at 300rpm for 1 hr and then at 1000 rpm for another 5 h. A white milkydispersion was formed. The dispersion was discharged, centrifuged,washed with MIBK and evaporated to dryness to afford 3.2 g (57% yield)of particles.

Example 15 Synthesis of Un-Encapsulated Core Particles from2-methylimidazole, DGEBA, and HyPox™ RK 84 (15)

The un-encapsulated core particles (15) were synthesized from 0.51 g ofthe CTBN-epoxy adduct of Example 2, 1.64 g (0.02 mole) of2-methylimidazole, 3.5 g (0.02 equivalent weight) DER™ 332, 15.3 g ofheptane and 34 g of MIBK using the procedure of Example 13. The reactionwas allowed to stir at 1000 rpm for 6 h under an argon atmosphere toafford 4.5 g (80% yield) of particles.

Example 16 Synthesis of Un-Encapsulated Core Particles from2-methylimidazole, DGEBA, and HyPox™ RK 84 (16)

The un-encapsulated core particles 16 were synthesized from 0.52 g ofthe CTBN-epoxy adduct of Example 2, 1.64 g (0.02 mole) of2-methylimidazole, 3.5 g (0.02 equivalent weight) DER™ 332, 2.6 g ofheptane and 49 g of MIBK using the procedure of Example 13 and thereaction was allowed to stir at 1000 rpm for 6 h under an argonatmosphere to afford 2.4 g (42.4% yield) of particles.

Example 17 Synthesis of Un-Encapsulated Core Particles from2-methylimidazole, DGEBA, and HyPox™ RK 84 (17)

The un-encapsulated core particles 17 were synthesized from 0.52 g ofthe CTBN-epoxy adduct of Example 2, 1.64 g (0.02 mole) of2-methylimidazole, 3.5 g (0.02 equivalent weight) DER™ 332, 10.2 g ofheptane and 41 g of MIBK using the procedure of Example 13. The reactionwas allowed to stir at 1000 rpm for 6 h under an argon atmosphere toafford 3.9 g (69% yield) of particles.

Example 18 Synthesis of Un-Encapsulated Core Particles from2-methylimidazole, DGEBA, and HyPox™ RK 84 (18)

A three-necked round bottom flask, equipped with a PTFE fluoropolymerhalf moon-shaped overhead stirrer, a reflux condenser, an additionfunnel, and an argon gas inlet was charged with 0.52 g of the CTBN-epoxyadduct of Example 2, 1.64 g (0.02 mole) of 2-methylimidazole, and 47.3 gof 4-methyl-2-pentanone (MIBK). The reactor was placed in an 80° C.bath, and purged with argon. After the reaction was allowed to stir at300 rpm for 1 hr, a solution of 3.5 g (0.02 equivalent weight) DER™ 332(a product of Dow Chemical) and 3.5 g of MIBK was added dropwise overthe course of 15 min, after which the reaction was allowed to stir at300 rpm for 1 h and then 1000 rpm for another 5 h. A white milkydispersion was formed. The dispersion was discharged, centrifuged,washed with MIBK, and evaporated to dryness to afford 4.53 g (80% yield)of particles.

Example 19 Synthesis Un-Encapsulated Core Particles from2-methylimidazole, DGEBA, and HyPox™ RK 84 (19)

The un-encapsulated core particles 19 were synthesized from 0.51 g ofthe CTBN-epoxy adduct of Example 2, 1.64 g (0.02 mole) of2-methylimidazole, 3.5 g (0.02 equivalent weight) DER™ 332, and 51 g ofMIBK using the procedure of Example 13 and the reaction was allowed tostir at 1500 rpm for 6 h under an argon atmosphere to afford 4.05 g(71.5% yield) of particles.

Example 20 Synthesis of Un-Encapsulated Core Particles from2-methylimidazole, DGEBA, and HyPox™ RK 84 (20)

The un-encapsulated core particles 20 were synthesized from 0.52 g ofthe CTBN-epoxy adduct of Example 2, 1.64 g (0.02 mole) of2-methylimidazole, 3.5 g (0.02 equivalent weight) DER™ 332, 7.6 g ofheptane, and 43 g of MIBK using the procedure of Example 13 and thereaction was allowed to stir at 1000 rpm for 6 h to afford 4.05 g (71.5%yield) of particles.

Example 21 Synthesis of Un-Encapsulated Core Particles from2-methylimidazole, DGEBA, and HyPox™ RK 84 (21)

The un-encapsulated core particles 21 were synthesized from 0.51 g ofthe CTBN-epoxy adduct from Example 2, 1.65 g (0.02 mole) of2-methylimidazole, 3.5 g (0.02 equivalent weight) DER™ 332, 7.6 g ofheptane and 43 g of MIBK using the procedure of Example 13. The reactionwas allowed to stir at 1000 rpm for 16 h to afford 3.6 g (64% yield) ofparticles.

Example 22 Synthesis of Un-Encapsulated Core Particles from2-methylimidazole, DGEBA, and HyPox™ RK 84 (22)

The un-encapsulated core particles 22 were synthesized from 0.51 g ofthe CTBN-epoxy adduct from Example 2, 1.64 g (0.02 mole) of2-methylimidazole, 3.85 g (0.022 equivalent weight) DER™ 332, 7.6 g ofheptane, and 43 g of MIBK using the procedure of Example 13. Thereaction was allowed to stir at 1000 rpm for 6 h under an argonatmosphere to afford 4.95 g (82.3% yield) of particles. A small drop ofthe dispersion was diluted with MIBK, coated on glass slide, and driedunder vacuum at room temperature. The dried sample was sputtered with athin layer of gold and its electron micrograph (FIG. 1 and FIG. 2) takenwith a Hitachi S-2460N scanning electron microscope.

Example 23 Synthesis of Un-Encapsulated Core Particles from2-methylimidazole, DGEBA, and HyPox™ RK 84 (23)

The un-encapsulated core particles 23 were synthesized from 0.51 g ofthe CTBN-epoxy adduct from Example 2, 1.64 g (0.02 mole) of2-methylimidazole, 3.85 g (0.022 equivalent weight) DER™ 332, 7.6 g ofheptane and 42 g of MIBK using the procedure of Example 13. The reactionwas allowed to stir at 1000 rpm for 16 h to afford 4.49 g (74.7% yield)of particles.

Examples for the Encapsulation of the Un-Encapsulated Core ParticlesExample 24 Encapsulated Particles from 2-methylimidazole, DGEBA, HyPox™RK 84, and MDI (24)

The microcapsule core was synthesized from 0.52 g of the CTBN-epoxyadduct from Example 2, 1.64 g (0.02 mole) of 2-methylimidazole, 3.85 g(0.022 equivalent weight) DER™ 332, 7.6 g of heptane and 42 g of MIBKusing the procedure of Example 13. The reaction was allowed to stir at1000 rpm for 6 h under an argon atmosphere. A small drop of thedispersion was removed, diluted with MIBK, coated on glass slide, anddried under vacuum at room temperature. The dried sample wassputter-coated with a thin layer of gold and the electron micrographtaken with a Hitachi S-2460N scanning electron microscope. Theencapsulation was started by adding a solution of 1.56 g (0.0125equivalent weight) of 4,4′-Methylenebis(phenyl isocyanate), mostcommonly referred to as MDI, and 14.1 g of MIBK, which was addeddropwise over the course of 110 min, after which the reaction wasallowed to stir at 1000 rpm for 15 h under an argon atmosphere. A smalldrop of the dispersion was dried and its FT-IR spectrum showed completeconversion of the isocyanate moiety. After it was confirmed all of theisocyanate had been consumed, a small drop of the dispersion wasremoved, diluted with additional MIBK, coated on glass slide, and driedunder vacuum at room temperature. The dried sample was sputtered with athin layer of gold and its electron micrograph taken with a HitachiS-2460N scanning electron microscope (FIG. 3 and FIG. 4).

Example 25 Synthesis Microcapsules from 2-methylimidazole, DGEBA, HyPox™RK 84, MDI, and 4,4′-Methylenebis(N,N-diglycidylaniline) (25)

The microcapsule core was synthesized from 0.51 g of the CTBN-epoxyadduct from Example 2, 1.64 g (0.02 mole) of 2-methylimidazole, 3.85 g(0.022 equivalent weight) DER™ 332, 7.6 g of heptane and 42 g of MIBKusing the procedure of Example 13 and the reaction was allowed to stirat 1000 rpm for 6 hr under an argon atmosphere. The encapsulation wasstarted by adding a solution of 1.4 g (0.0112 equivalent weight) of MDI,0.16 g (0.00038 equivalent weight) of4,4′-Methylenebis(N,N-diglycidylaniline), and 14.1 g of MIBK, which wasadded dropwise over the course of 110 min, after which the reaction wasallowed to stir at 1000 rpm for 15 h under an argon atmosphere. A smalldrop of dispersion was dried and its FT-IR spectrum showed completeconversion of the isocyanate moiety.

Example 26 Synthesis of Microcapsules from 2-methylimidazole, DGEBA,HyPox™ RK 84, and MDI (26)

The microcapsule core was synthesized from 0.52 g of the CTBN-epoxyadduct from Example 2, 1.64 g (0.02 mole) of 2-methylimidazole, 3.86 g(0.022 equivalent weight) DER™ 332, 7.6 g of heptane, and 42 g of MIBKusing the procedure of Example 13. The reaction was allowed to stir at1000 rpm for 6 h under an argon atmosphere. The encapsulation wasperformed by the addition of a solution of 1.57 g (0.0125 equivalentweight) of MDI and 14.1 g of MIBK, which was added dropwise over thecourse of 90 min, after which the reaction was allowed to stir at 1000rpm for 15 h under an argon atmosphere. A small drop of dispersion wasdried and its FT-IR spectrum showed complete conversion of theisocyanate moiety.

Example 27 Synthesis of Microcapsules from 2-methylimidazole, DGEBA,HyPox™ RK 84, MDI, and 4,4′-Methylenebis(N,N-diglycidylaniline) (27)

The microcapsule core was synthesized from 0.52 g of the CTBN-epoxyadduct from Example 2, 1.64 g (0.02 mole) of 2-methylimidazole, 3.85 g(0.022 equivalent weight) DER™ 332, 7.6 g of heptane and 43 g of MIBKusing the procedure of Example 13 and the reaction was allowed to stirat 1000 rpm for 6 hr under an argon atmosphere. The encapsulation wasstarted by adding a solution of 2.8 g (0.0223 equivalent weight) of MDI(a product of Sigma Aldrich), 0.35 g (0.0033 equivalent weight) of4,4′-Methylenebis(N,N-diglycidylaniline), and 14.1 g of MIBK, which wasadded dropwise over the course of 240 min, after which the reaction wasallowed to stir at 1000 rpm for 15 h under an argon atmosphere.

Example 28 Synthesis of Microcapsules from 2-methylimidazole, DGEBA,HyPox™ RK 84, MDI, and 4,4′-Methylenebis(N,N-diglycidylaniline) (28)

A three-necked round bottom flask, equipped with a PTFE fluoropolymerhalf moon-shaped overhead stirrer, a reflux condenser, an additionfunnel, and an argon gas inlet was charged with 1.03 g of the CTBN-epoxyadduct from Example 2, 3.28 g (0.04 mole) of 2-methylimidazole, 15.2 gof heptane and 76 g of 4-methyl-2-pentanone (MIBK). The reactor wasplaced in an 80° C. bath and purged with argon. After 1 hr, a solutionof 7.7 g (0.044 equivalent weight) DER™ 332 (a product of Dow Chemical)and 7.7 g of MIBK was added drop wise over the course of 40 min, afterwhich the reaction was allowed to stir at 1000 rpm for 6 hr under anargon atmosphere. A white milky dispersion was formed. A small drop ofthe dispersion was diluted, coated on glass slide and dried in vacuumoven at room temperature. The dried sample was sputtered with a thinlayer of Au and taken scanning electron micrographs. The encapsulationwas started by adding a solution of 2.8 g (0.0223 equivalent weight) ofMDI, 0.32 g (0.003 equivalent weight) of4,4′-Methylenebis(N,N-diglycidylaniline), and 28.2 g of MIBK, which wasadded dropwise over the course of 240 min, after which the reaction wasallowed to stir at 1000 rpm for 12.5 hr under an argon atmosphere.

Example 29 Synthesis of Microcapsules from 2-methylimidazole, DGEBA,HyPox™ RK 84L, Desmodur® W, and 4,4′-Methylenebis(N,N-diglycidylaniline)(29)

A three-necked round bottom flask, equipped with a PTFE fluoropolymerhalf moon-shaped overhead stirrer, a reflux condenser, an additionfunnel, and an argon gas inlet was charged with 2.09 g of the CTBN-epoxyadduct from Example 2, 6.56 g (0.08 mole) of 2-methylimidazole and 183 gof 4-methyl-2-pentanone (MIBK). The reactor was placed in an 80° C. bathand purged with argon. After 1 hr, a solution of 15.4 g (0.088equivalent weight) DER™ 332 (diglycidyl ether of bisphenol A (DGEBA)from Dow Chemical) and 18.7 g of MIBK was added drop wise over thecourse of 1 hr, after which the reaction was allowed to stir at 1000 rpmfor 6 hr under an argon atmosphere. A white milky dispersion was formed.The particles were allowed to precipitate under gravity allowing thesupernatant liquid was removed by decantation. The particles wereredispersed in MIBK. The residual dispersion was filtered through asmall pore size membrane filter. The particles were redispersed in MIBKand then filtered through a 30 μm pore size filter to remove large-sizedparticles and aggregates. A few drops of the resulting dispersion weredried, sputtered with gold, loaded into an SEM. Its micrograph showedthe particles were of adequate quality to be allowed to proceed on tothe encapsulation step. The solid content of the dispersion was measuredat 9.84% (w/w). The yield of total dispersion was 84.4 g.

A three-neck round bottom flask, equipped with a PTFE fluoropolymer halfmoon-shaped overhead stirrer, a reflux condenser, an addition funnel,and an argon gas inlet was charged with 0.83 g of the CTBN-epoxy adductfrom Example 2, 10.3 g of MIBK, and the purified dispersion. The reactorwas placed in an 80° C. bath and purged with argon. To this, 17 g ofheptane was added drop-wise over the course of 1 hr. The encapsulationwas started by adding a solution of 1.9 g (0.0145 equivalent weight) ofDesmodur® W (a liquid cycloaliphatic diisocyanate from BayerMaterialScience), 0.19 g (0.002 equivalent weight) of4,4′-Methylenebis(N,N-diglycidylaniline), and 18.9 g of MIBK, which wasadded drop-wise over the course of 4 hr, after which the reaction wasallowed to stir at 1000 rpm for 12.5 hr under an argon atmosphere.

Example 30 (Prophetic) Synthesis of Microcapsules Comprised of Two ShellMaterials

A three-necked round bottom flask, equipped with a PTFE fluoropolymerhalf moon-shaped overhead stirrer, a reflux condenser, an additionfunnel, and an argon gas inlet is charged with 2.09 g of the CTBN-epoxyadduct from Example 2, 6.56 g (0.08 mole) of 2-methylimidazole and 183 gof 4-methyl-2-pentanone (MIBK). The reactor is placed in an 80° C. bathand purged with argon. After 1 hr, a solution of 15.4 g (0.088equivalent weight) DER™ 332 (a product of Dow Chemical) and 18.7 g ofMIBK is added drop-wise over the course of 1 hr, after which thereaction is allowed to stir at 1000 rpm for 6 hr under an argonatmosphere. A white milky dispersion is formed. The particles areallowed to precipitate under gravity allowing the supernatant liquid tobe removed by decantation. The particles are redispersed in MIBK. Theresidual dispersion is filtered through a small pore size membranefilter. The particles are redispersed in MIBK and then filtered througha 30 μm pore size filter to remove large-sized particles and aggregates.

A three-neck round bottom flask, equipped with a PTFE fluoropolymer halfmoon-shaped overhead stirrer, a reflux condenser, an addition funnel,and an argon gas inlet is charged with 0.83 g of the CTBN-epoxy adductfrom Example 2, 10.3 g of MIBK, and the purified dispersion. The reactoris placed in an 80° C. bath and purged with argon. To this, 17 g ofheptane is added drop-wise over the course of 1 hr. The encapsulationwith the first shell layer was started by adding a solution of 1.9 g(0.0145 equivalent weight) of Desmodur® W (a product of BayerMaterialScience), 0.19 g (0.002 equivalent weight) of4,4′-Methylenebis(N,N-diglycidylaniline), and 18.9 g of MIBK is addeddrop-wise over the course of 4 hr, after which the reaction is allowedto stir at 1000 rpm for 12.5 hr under an argon atmosphere.

The second shell layer is formed by the addition of a solution of 1.9 g(0.0145 equivalent weight) of Desmodur® W (a product of BayerMaterialScience), 0.19 g (0.002 equivalent weight) of4,4′-Methylenebis(N,N-diglycidylaniline), and 18.9 g of MIBK is addeddrop-wise over the course of 4 hr, after which the reaction is allowedto stir at 1000 rpm for 12.5 hr under an argon atmosphere.

Example 31 (Prophetic) Synthesis of Microcapsules Comprised of Two ShellMaterials, where the Outermost Shell Material is Comprised of an EpoxyCompatible Material

A three-necked round bottom flask, equipped with a PTFE fluoropolymerhalf moon-shaped overhead stirrer, a reflux condenser, an additionfunnel, and an argon gas inlet is charged with 2.09 g of the CTBN-epoxyadduct from Example 2, 6.56 g (0.08 mole) of 2-methylimidazole and 183 gof 4-methyl-2-pentanone (MIBK). The reactor is placed in an 80° C. bathand purged with argon. After 1 hr, a solution of 15.4 g (0.088equivalent weight) DER™ 332 (a product of Dow Chemical) and 18.7 g ofMIBK is added drop-wise over the course of 1 hr, after which thereaction is allowed to stir at 1000 rpm for 6 hr under an argonatmosphere. A white milky dispersion is formed. The particles areallowed to precipitate under gravity allowing the supernatant liquid tobe removed by decantation. The particles are redispersed in MIBK. Theresidual dispersion is filtered through a small pore size membranefilter. The particles are redispersed in MIBK and then filtered througha 30 μm pore size filter to remove large-sized particles and aggregates.

A three-neck round bottom flask, equipped with a PTFE fluoropolymer halfmoon-shaped overhead stirrer, a reflux condenser, an addition funnel,and an argon gas inlet is charged with 0.83 g of the CTBN-epoxy adductfrom Example 2, 10.3 g of MIBK, and the purified dispersion. The reactoris placed in an 80° C. bath and purged with argon. To this, 17 g ofheptane is added drop-wise over the course of 1 hr. The first shelllayer encapsulation was started by adding a solution of 1.9 g (0.0145equivalent weight) of Desmodur® W (a product of Bayer MaterialScience),0.19 g (0.002 equivalent weight) of4,4′-Methylenebis(N,N-diglycidylaniline), and 18.9 g of MIBK is addeddrop-wise over the course of 4 hr, after which the reaction is allowedto stir at 1000 rpm for 12.5 hr under an argon atmosphere.

The second shell layer is formed by the addition of a solution of 1.9 g(0.0145 equivalent weight) of Desmodur® W (a product of BayerMaterialScience), 1.9 g of CVC Thermoset Materials HyPox™ RA1340, and18.9 g of MIBK is added drop-wise over the course of 4 hr, after whichthe reaction is allowed to stir at 1000 rpm for 12.5 hr under an argonatmosphere.

Example 32 (Prophetic) Synthesis of Microcapsules Comprised of Two ShellMaterials, where the Outermost Shell Material is Comprised of an EpoxyCompatible Material

A three-necked round bottom flask, equipped with a PTFE fluoropolymerhalf moon-shaped overhead stirrer, a reflux condenser, an additionfunnel, and an argon gas inlet is charged with 2.09 g of the CTBN-epoxyadduct from Example 2, 6.56 g (0.08 mole) of 2-methylimidazole and 183 gof 4-methyl-2-pentanone (MIBK). The reactor is placed in an 80° C. bathand purged with argon. After 1 hr, a solution of 15.4 g (0.088equivalent weight) DER™ 332 (a product of Dow Chemical) and 18.7 g ofMIBK is added drop-wise over the course of 1 hr, after which thereaction is allowed to stir at 1000 rpm for 6 hr under an argonatmosphere. A white milky dispersion is formed. The particles areallowed to precipitate under gravity allowing the supernatant liquid tobe removed by decantation. The particles are redispersed in MIBK. Theresidual dispersion is filtered through a small pore size membranefilter. The particles are redispersed in MIBK and then filtered througha 30 μm pore size filter to remove large-sized particles and aggregates.

A three-neck round bottom flask, equipped with a PTFE fluoropolymer halfmoon-shaped overhead stirrer, a reflux condenser, an addition funnel,and an argon gas inlet is charged with 0.83 g of the CTBN-epoxy adductfrom Example 2, 10.3 g of MIBK, and the purified dispersion. The reactoris placed in an 80° C. bath and purged with argon. To this, 17 g ofheptane is added drop-wise over the course of 1 hr. The encapsulationwas started by adding a solution of 1.9 g (0.0145 equivalent weight) ofDesmodur® W (a product of Bayer MaterialScience), 0.19 g (0.002equivalent weight) of 4,4′-Methylenebis(N,N-diglycidylaniline), and 18.9g of MIBK is added drop-wise over the course of 4 hr, after which thereaction is allowed to stir at 1000 rpm for 12.5 hr under an argonatmosphere.

The second shell layer is formed by the addition of a solution of 1.9 g(0.0145 equivalent weight) of Desmodur® W (a product of BayerMaterialScience), 1.9 g of Toagosei GP-301 graft polyacrylate, 0.19 g(0.002 equivalent weight) of 4,4′-Methylenebis(N,N-diglycidylaniline),and 18.9 g of MIBK is added drop-wise over the course of 4 hr, afterwhich the reaction is allowed to stir at 1000 rpm for 12.5 hr under anargon atmosphere.

Examples for the Preparation of the Masterbatch Example 33 Preparationof the Masterbatch from the Particles of Example 24

The dispersion of the particles of Example 24 were evaporated undervacuum at 50° C. to obtain a yellow solid, ground with a mortar andpestle, and added to diglycidyl ether of bisphenol A in a ratio of 35:65(w/w) particles to epoxy resin. The mixture was dispersed for 20 minusing a three roll mill to obtain a creamy yellow dispersion.

Example 34 Preparation of the Masterbatch from the Particles of Example28

At room temperature, 10 g of diglycidyl ether of bisphenol A was addedto the reaction mixture of Example 28, which contained the dispersion ofthe particles, and stirred for 3 hr. The solvent was removed undervacuum at 31° C. to a solids content of 86% (w/w). From this, 12.86 gwas removed and mixed with and additional 7.90 g of diglycidyl ether ofbisphenol A. The mixture was then process further for 3 min using athree-roll mill to obtain a creamy yellow dispersion.

Performance Results:

For the solvent resistance test, mixtures were prepared by combining theparticles, diglycidyl ether of bisphenol A, and MIBK in a ratio of4:50:46 (w/w). The mixtures were then placed in a 40° C. oil bath andmonitored visually for a change in viscosity. The results are shownbelow in Table 1. Aliquots of the mixtures above were coated on glassslides as thin films and dried under vacuum at room temperature. DSCtraces were obtained using a TA Instruments Q10 Differential Scanningcalorimeter using a temperature window of 30 to 250° C., a heating rateof 5° C./min, and performed under a nitrogen atmosphere. The results areshown below in Table 1.

TABLE 1 The solvent resistance and DSC results of the un-encapsulatedand encapsulated particles: Solvent resistance and DSC results of theun-encapsulated and encapsulated particles Un- Solvent DSC encapsulated/resistance T_(peak) (exo, Particle Encapsulated Time to gel (h) ° C.) ΔH(J/g) 22 Un-encapsulated 14 105 297 24 Encapsulated 120 119 330 25Encapsulated 170 124 307 27 Encapsulated 240 142 200 28 Encapsulated 190124 218

Having described the invention in detail and by reference to specificembodiments thereof it will be apparent to those skilled in the art thatnumerous variations and modifications are possible without departingfrom the spirit and scope of the following claims.

1. A curing agent for epoxy resins that is comprised of the reactionproduct of: (a) an amine, and (b) an epoxy resin, and (c) anelastomer-epoxy adduct wherein the elastomer-epoxy adduct is acarboxyl-terminated butadiene-acrylonitrile (CTBN)-epoxy adduct whichfunctions as a dispersant; wherein the amine is reacted with thedispersant followed by the epoxy resin to produce a dispersion of epoxyresin particles; wherein the particles are encapsulated in a polymershell that is the reaction product of a multifunctional isocyanate and amultifunctional epoxy compound.
 2. The curing agent of claim 1 whereinthe nitrile content of the CTBN is about 12-35% by weight.
 3. The curingagent of claim 2 wherein the nitrile content is about 20-33% by weight.